The behaviour of ion orbits in the magnetic and electric fields at the centre of a cyclotron is studied in detail. The objective is to optimize the phase acceptance and beam quality for a 500 MeV H¯ isochronous cyclotron. Since accurate electric fields are necessary for orbit calculations, a numerical method for calculating these fields is examined in detail. The method is suitable for complicated electrode shapes and converges rapidly, yielding potentials in three dimensions with average errors of less than 0.01%. The magnetic fields used in the orbit calculations are measured on model magnets. The axial motions are examined using a thick lens approximation for the accelerating gaps. A method is demonstrated for calculating the axial acceptance of the cyclotron as a function of RF phase. This method is used to evaluate the merits of various central geometries and injection energies. This method is also used to examine the effects of flat-topping the RF voltage by adding some third harmonic to the fundamental waveform. It is found that addition of the optimum amount of third harmonic increases the phase acceptance by about 20 deg. Finally, the effects of field bumps on the axial motions are investigated. To allow accurate radial motion calculations to high energy, an approximate formula is developed which yields accurate (<1%) values for the changes in orbit properties of an ion crossing a dee gap. The geometry of the orbit on the first turn is discussed in detail. The radial centring is studied by tracking ions from injection to 20 MeV, and a method is described for choosing the starting conditions of the beam so as to minimize the radial betatron amplitude over a desired phase range. The problems associated with using a three-fold symmetric magnetic field with a two-fold symmetric electric field are also discussed. Besides the well-known gap-crossing resonance, a previously ignored phase-oscillation effect is found to be important for cyclotrons operating on a high harmonic of the ion rotation frequency. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The purpose of this thesis is to determine the effects of x-irradiation on the efflux of potassium, sodium and calcium ions from stimulated and unstimulated desheathed sciatic nerves.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Elastic scattering and inelastic excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) for the identical-particle fermionic system 9Be + 9Be have been measured at the highest incident beam energy presently available ELab(9Be) = 25 MeV. A 9Be beam, produced by the General Ionex Corporation model 860C sputter ion-source, was accelerated by the EN Tandem Van de Graaff accelerator of the iThemba LABS (Gauteng) and was used to bombard a thin 9Be target. The experimental equipment associated with the C-line includes a high resolution ΔE-E gas-ionisation detector coupled to a small scattering chamber. Energy loss and residual energy signals were processed using a CAMAC-based plus OS/2 WIMPS2 data acquisition system running on an online computer. The ΔE-E plots were used to identify the reaction products and their kinematic energies, thereby determining the elastic and inelastic scattering cross-sections. The elastic and inelastic scattering data were analysed in terms of the optical model and Distorted Wave Born Approximation, respectively. Angular distribution data for the elastic scattering for 9Be + 9Be conformed well to the optical model predictions using an energy-independent optical model potential. Inelastic scattering cross-sections were determined up to θc.m.  135° and symmetry effects were investigated. As such, excitation of the second, unbound, state 9Be (5/2ˉ, 2.43 MeV) via a strong E2 one-step two-body interaction from the 9Be (3/2ˉ, g.s.) did not show effects due to symmetry in the entrance channel. These results were consistent with a previous study at ELab(9Be) = 16 MeV.

Orientador: Pedro de Magalhães Padilha / Banca: Clóvis Augusto Ribeiro / Banca: Ana Rita de Araújo Nogueira / Resumo: Este trabalho descreve a síntese, a caracterização da celulose modificada com grupos p-aminobenzóico (Cel-PAB) e os resultados do estudo da capacidade de adsorção de Cd(II), Cu(II), Ni(II), Zn(II) e Pb(II) pelo novo adsorvente, em diferentes valores de pH e tempos de contato dinâmico. A caracterização da Cel-PAB foi feita por espectroscopia de absorção na região do infravermelho com transformada de Fourrie (FT-IR), análise elementar de nitrogênio e determinação da área superficial específica. A capacidade máxima de sorção de íons metálicos pela Cel-PAB, determinada pelo método de sorção em batelada, foi da ordem de 2,00 mmol g-1 para os íons metálicos estudados. A pré-concentração de soluções analíticas dos metais com posterior eluição e leitura dos eluatos por espectrometria de absorção atômica por chama (FAAS), possibilitou a diminuição do limite de detecção (L. D.), o que permitiu a determinação dos metais presentes em baixas concentrações. O sistema desenvolvido para pré-concentração de íons metálicos foi aplicado em amostras de águas naturais, mineralizadas e não mineralizadas, da represa de Barra Bonita/Rio Tietê-SP e as determinações foram feitas por FAAS. Esses resultados foram comparados com aqueles obtidos por espectrometria de absorção atômica em forno de grafite (FGAAS) nas mesmas amostras de água. Diferenças significativas não foram encontradas, o que demonstrou a aplicabilidade do sistema proposto. / Abstract: This work describes the synthesis, characterization of the modified cellulose with p-amino benzoic groups (Cel-PAB) and the results of the study of adsorption capacity from ions Cd (II), Cu (II), Ni (II), Zn (II) and Pb (II) by new adsorbent, in different pH values and dynamic contact times. The characterization of Cel-PAB was performed by FT-IR, elemental analysis of N2 and determination of the specific surface area. The maximum adsorption capacity of all metal ions by the Cel-PAB, determined by batch adsorption procedure, was approximately 2.00 mmol g-1 for studied metal ions. The pre-concentration in analytical metal ions solutions with further elution and read-out of elutes by flame atomic absorption spectrometry (FAAS), improve the detection limit (D.L.) allowing the detection of small amount of cations. The metal ions preconcentration system developed was applied in natural mineralized and non mineralized waters samples from Barra Bonita weir/Tietê River-SP and the analysis was carried out by FAAS technique. These results were compared with those obtained by atomic absorption spectrometry in graphite furnace (FGAAS) in the same sample waters. Small differences were not observed showing the applicability of the proposed system. / Mestre

Adverse tissue reactions to hip prostheses containing CoCr alloys have been widely reported, particularly for implants utilising a metal-on-metal bearing surface or, more recently, a modular taper junction and have been termed Adverse Response to Metal Debris (ARMD). Histological assessments of synovial tissues from patients at revision operation often demonstrate an extensive accumulation of macrophages and abundant tissue necrosis or fibrosis. The inflammatory response starts with the recruitment of immune cells and requires the egress of macrophages from the inflamed site for resolution of the reaction. Metal particles have previously been shown to affect cell migration but the effects of cobalt and chromium on macrophages' motility remain largely unknown. In vitro and in vivo macrophage migration during exposure to cobalt and chromium ions and nanoparticles were examined in this thesis. Cobalt, but not chromium, was found to significantly reduced macrophage motility (>50%). This was found to involve an increase in both cell spreading and the formation of intracellular podosome-type adhesion structures, as well as enhanced cell adhesion to the extracellular matrix (ECM). The formation of podosomes was also associated with the production and activation of matrix metalloproteinase-9 (MMP9) and enhanced ECM degradation. These effects were driven by the down-regulation of RhoA signalling through the generation of reactive oxygen species (ROS). The effect of the Co2+ and Cr3+ metal ions on tissue remodelling and pseudotumour formation which can lead to pain, swelling, limited range of joint movement and extensive tissue lesions, was explored using a multiscale approach. Both 2D and 3D in vitro culture systems were deplored to examine the effects of these ions on human fibroblast activation and mechanobiology. It was observed that Co2+ induced a fibrotic response characterised by cytoskeletal remodelling and enhanced collagen matrix contraction. This was associated with an increase in cell stiffness (~45%) and contractile forces (~80%) measured by atomic force microscopy and traction force microscopy, respectively. These effects were also triggered by the generation of ROS. Moreover, this fibrotic response was enhanced in the presence of macrophages, which increased the prevalence of α-SMA positive fibroblasts and collagen synthesis. These events were verified in vivo by examining the synovial fibroblasts and tissues from hips of patients with metal-on-metal hip implants and patients undergoing primary hip replacement. The findings revealed that fibroblasts isolated from patients undergoing MoM revision THA were more biomechanically active than the control group. Moreover, synovial tissues from patients undergoing MoM revision THA displayed evidence of extensive tissue remodelling and fibrosis. These findings revealed that cobalt leads to adverse tissue reactions via inducing macrophage retention, fibroblast-mediated matrix remodelling and modulating the interplay between macrophage and fibroblast. These distinctive effects can help us understand the pathogenesis of ARMD and the cellular response to cobalt-based alloys, which will inform biocompatibility test protocols and future implant designs.

Typescript (photocopy) / x, 110 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1983